Seriously need help, wierd Voltage issue

[Schmieder]

Hard start, really rough idle then dies moments later. Brand new battery, fully charged but voltage drops to low during the rough idle. In the range of 5.5 to 11.5 volts during the really rough idle.

Battery in the trunk has same voltage as starter. Both grounds on the trans housing are good, ground on battery is good and practically zero resistance in the positive cable to the starter and the positive post.

Batt ground is good
Engine grounds seem fine (jumped them to the frame, no difference)

Volts drop during crank and do not go past 11.5 before stalling out.

Here is the scan of the hard start. See the volts? This is buggering the crap out of me.


I am in need of help, please.




edit: I have been chasing down all kinds of potential problems. The car sat for 8 months and then had a dying pump. Get past that issue and now, today I finally got the engine to run long enough to get a decent scan. Had the battery fully charged and that prevented the log from stopping (lack of volts during crank stops the logging).

So now I see this voltage issue and I already checked the electrical system as best I knew how too.

How does the alternator ground? Which bolt does it ground through or both?

AAHHhhh, the stress is mounting!

[bob442]

alt. should ground threw the block. same with starter. check your engine ground again. sounds like your PCM *could be killing the car from lack of voltage. where did this car sit for 8 months? bottom of the sea?

[Schmieder]

alt. should ground threw the block. same with starter. check your engine ground again. sounds like your PCM *could be killing the car from lack of voltage. where did this car sit for 8 months? bottom of the sea?

Bottom of the sea, lol. Driveway in Pittsburgh PA. Parked in winter and sat into the warm months recently. There were circumstances to the failing pump, the filter was deteriorating and the time sitting probably made it worse, the pump sucked up filter pieces. That has since been replaced and tank flushed.

I had also swapped the transmission as well. Put in a getrag282. I kept the grounds bolted to the bell housing in the same spot, but new trans. They tested as good and I even tried jumping them to the frame as well. The frame has a great ground too.

I'm going to try to ground the engine to the frame again and see if that changes anything.

But I already ran a jumper from the exhaust where it has a clean connection to the block onto the frame.



What if I just upgraded the 5 major ground points? (except for Batt to chassis, that has a new heavy duty cable and tested great)
Battery to Engine
Battery to Chassis
Engine to Chassis
Engine to Subframe
Subframe to Chassis

Maybe I'll do that and then see what happens, along with jumping the alternator ground direct to the engine block AND frame.

Maybe the getrag bell housing doesn't like to conduct? But then the bolt should thread into the block and ground out there too.

[tractorman]

Battery in the trunk has same voltage as starter. Both grounds on the trans housing are good, ground on battery is good and practically zero resistance in the positive cable to the starter and the positive post.

Not sure if I understand you correctly. Have you re-located the battery to the trunk? If so, where are the cables ran to & hooked up?

[Schmieder]

Yes, trunk mounted battery. Has full housing, straps and steel braces. A very nice setup.

Positive is routed to the starter post and the original stock positive cable was kept in for the rest of the routing. Negative is bolted well to the frame, ground to bare metal and bolted tight. All the areas I tested for resistance come back 0.1 Ohms, which is the same resistance reading I get with new copper at 1" distance.

That trunk mount has been fully functional for months before the manual swap. Nothing changed except the manual trans swap since the last time it ran great, 8 months ago. Well, except for a new PCM and new fuel pump. I tried new spark plugs as well, incase I fouled the others. Removed ALL the old gas for fresh gas.

I remember when I first turned the key, my aftermarket gauges lit up dimmly then faded to nothing and hasn't lit up since. I have removed them as well and returned any electrical work back to stock. Which was only a constant battery tap and a key/on/run tap with seperate grounds from the rest of the cars grounding system. I tried the fan relays in place of the ignition relays, forced the pump on constant during crank with HPT. Tried various AFR adjustment.....but the bottom line seems to be a very bad voltage drop.

Recap, I made no changes to my electrical system since it ran fine except for the YEL+ PPL P/N switch spliced.

I did have the VSS and the 7xCPS or 3xCPS (manual says both, lol) mixed up. But they both operate in principle the same and under equal voltages. So there couldnt have been damage, and HP Scanner is showing the PCM dictate spark properly during crank.

It's the darn voltage drop, what a royal PITA!!!!!!! I'm about ready to tow it to a shop. I am a mechanical wiz at heart, I love electronics too but this is getting beyond me. And to top everything off, my DVM just died today.

[Azrael]

Check for resistance between the positive battery cable and the chassis. It sounds to me like the electrical system is shorting out somewhere.

[Schmieder]

Check for resistance between the positive battery cable and the chassis. It sounds to me like the electrical system is shorting out somewhere.

That is a great idea, wish I thought of that before my DVM died today. (not being sarcastic, it really did die today)

Come to think of it, the battery does drain faster then normal. Not draining while sitting, that is fine. But a short while key/on could really be a real possibility. I did notice I have fewer start attempts per charge. I checked for parasitic drain while key/off, wish I thought twice to check resistance from Battery to chassis then.

Any idea what amount of resistance would be considered normal while Key/On/Run position?

I gotta say Azrael, I'm glad you mentioned this. I have some hope now. I just need to get a new DVM and track down the culprit circuit. Spend a day pulling fuses while reading the DVM.

Now, I noticed burnt copper wire at the lower trans mounted ground. Would be bolted to the bolt that secures the trans bell housing to the block. The wire was sitting between the negative cable and the housing, crunched and seemed to restrict the grounding ability of the neg cable. Even though fixing that didn't solve the issue, I bet the short is shorting through that ground wire.

Hey, thanks man! This idea really lifted my spirits!

[1988GTU]

What gauge wire did you use with relocation?

[Schmieder]

What gauge wire did you use with relocation?

Not sure but it was a kit for trunk mounted batteries. The cables are about as thick as a AA Battery. Plus, it was working just fine before the manual swap. I remember getting 13.5-14.2 volts at idle from log files. I thought I may have tugged the cable and damaged a connection but I since tested that.

I also augmented the batt+ with a jump to the positive post in the engine bay (adding a bypass cable). No difference.

I had determined the + cable is fine. 0.1 Ohms, termianls clean, doesn't heat up, and additional jumpers to augment the cable make no difference.

I'm thinking there may be a short under the dash as that is the only area where wires were shifted to make room for the clutch pedal swing.

Or the clutch pedal is pinching a wire open.

Whatever it is, I have a day of fuse pulling. Now I just need to replace my volt meter.

[robertisaar]

since this might not have been explained completely:

the case of the alternator is it's ground. and anything connected to the alt case(and down the line as well) needs to be corrosion free and tight, otherwise you will have issues.

[Schmieder]

since this might not have been explained completely:

the case of the alternator is it's ground. and anything connected to the alt case(and down the line as well) needs to be corrosion free and tight, otherwise you will have issues.

Yeah, the alternator was wire wheeled at high rpm's and it opened up clean metal real nice (where it grounds to the frame). Same with the frame contacts, bolts/nuts, positive terminals, etc. All the bolt down heavy gauge cables were thoroughly wired down to fresh metal. I also added a ground wire from the alternator ground to the block.


I learned something interesting yesterday. Dielectric grease doesn't conduct electricity. It does, however, have a fantastic penetration value. Meaning the two conductive surfaces can easily push the grease away and make a strong electrical contact as if there were no dielectric grease present. What it does is help prevent corrosion and keep filth away from the vital conductive surfaces. So the grease is actually a corrosion prevention material and not a current enhancement.

Pretty neat ehh?

Thanks Rob, you are one of the fewer who really helped me out through this project. When I make the final show-off video, I will dedicate you and few others here, true professionals.

[pocket-rocket]

I learned something interesting yesterday. Dielectric grease doesn't conduct electricity. It does, however, have a fantastic penetration value. Meaning the two conductive surfaces can easily push the grease away and make a strong electrical contact as if there were no dielectric grease present. What it does is help prevent corrosion and keep filth away from the vital conductive surfaces. So the grease is actually a corrosion prevention material and not a current enhancement.

Taken from wiki:

A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric polarization.

That's also why I use it on any light bulbs or spark plug wires I do. To keep the electrical connection protected and keep corrosion inducing moisture out. I've had connections go bad enough from corrosion that melted the plug the wires were in. I had to cut the plug off of the blower motor resistor for the heater in my truck because of it. I got lucky enough that since the connection had gone bad enough to eat half of one of the terminal, but still allow enough current to move to heat the plug up to the melting point but nothing shorted out and caught fire. Now it's got regular crimp on spade terminals with a small layer of dielectric grease. If I were to do it over the only change would be solder on terminals, but crimp on is what I had around and I'm not using my heat right now, lol.

[Azrael]

I'm glad I got you on the right track. Pulling the fuses to troubleshoot was a really good idea that I'll have to remember. Definitely use any wiring diagrams you have for your car even if only to mark off wires/circuits you've tested to be good.

[tractorman]

Is there a good ground cable between the frame and the engine? Did you disturb any cable connections when you did the transmission swap?

[Schmieder]

Taken from wiki:

A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric polarization.

That's also why I use it on any light bulbs or spark plug wires I do. To keep the electrical connection protected and keep corrosion inducing moisture out. I've had connections go bad enough from corrosion that melted the plug the wires were in. I had to cut the plug off of the blower motor resistor for the heater in my truck because of it. I got lucky enough that since the connection had gone bad enough to eat half of one of the terminal, but still allow enough current to move to heat the plug up to the melting point but nothing shorted out and caught fire. Now it's got regular crimp on spade terminals with a small layer of dielectric grease. If I were to do it over the only change would be solder on terminals, but crimp on is what I had around and I'm not using my heat right now, lol.

I used dielectric grease on my connectors. Not major ones like battery terminals, I keep them clean, flat and well tight. I hope to get some heat shrink over them when I got it running good.

I'm glad I got you on the right track. Pulling the fuses to troubleshoot was a really good idea that I'll have to remember. Definitely use any wiring diagrams you have for your car even if only to mark off wires/circuits you've tested to be good.

I have Alldata for my car so I have access to every electrical diagram I need. I am putting together a graphic map so I can effectively test every point possible and find this pita short. Now I know, now it's time to get the job done and WOT off into the sunset....haha

Is there a good ground cable between the frame and the engine? Did you disturb any cable connections when you did the transmission swap?

Batt (-) to chassis is good and strong. Every ground has been Ohm tested with very little resistance, equal to 1" of clean thick copper. The low resistance was impressive for the long positive cable running to the engine bay. I paid good money for that kit, the original ground failed but the positive cable is quite remarkable. Much thicker then any stock cable I've ever seen.

I also tested the ground resistance between all 5 major ground points. Basically the wiring is great except for the short./

The only instance I can find of a short on the neutral charged terminal of the fuse is the coolant fans 1&2. Though many systems had shorted power feeds, the hot side of the fuse, all key-on. So I believe I trace the fans wires and I will find the short.

Well see, I am just starting my plan of attack. I have to hit the diagrams hard and get to know the circuits well.